1. Field of the Invention
The present invention relates to a semiconductor device and its testing method.
2. Description of Related Art
A burn-in test has been known as a reliability test of a semiconductor device. Among the burn-in tests, there are a static burn-in test and a dynamic burn-in test. For example, Patent document 1 (Japanese Unexamined Patent Application Publication No. 05-251534) discloses a technique to test the reliability of a semiconductor device with efficiency by alternately performing a dynamic burn-in test and a static burn-in test.
FIG. 6 shows a block diagram illustrating a semiconductor device disclosed in Patent document 1. As shown in FIG. 6, an input terminal 405 is connected to a signal line 413. Further, an input terminal 406 is connected to a signal line 414. Further, the signal lines 413 and 414 are connected to input terminals of a first internal circuit 403. Further, input terminals 407 and 408 are connected to signal lines 415 and 416 respectively. Further, the signal lines 415 and 416 are connected to input terminals of a second internal circuit 404. Further, the signal lines 413, 414, 415 and 416 are also connected to output terminals of a switch circuit 402. Further, an oscillation circuit 401 is connected to input terminals of the switch circuit 402.
During a normal operation, external signals are input to the input terminals 405, 406, 407 and 408. Meanwhile, during a burn-in test, the input terminals 405, 406, 407 and 408 are in an open state.
Further, the oscillation circuit 401 stops its operation during the normal operation, whereas it oscillates during the burn-in test.
Further, during the burn-in test, the switch circuit 402 switches between a state where an output signal of the oscillation circuit 401 is propagated to the signal lines 413 and 414 while the signal lines 415 and 416 are fixed at a ground level and a state where an output signal of the oscillation circuit 401 is propagated to the signal lines 415 and 416 while the signal lines 413 and 414 are fixed at a ground level. Further, the switch circuit 402 puts the signal lines 413, 414, 415 and 416 into a high-impedance state during the normal operation.
During the burn-in test, when the switch circuit 402 is switched and set to a state where the output signal of the oscillation circuit 401 is propagated to the signal lines 413 and 414, the first internal circuit 403 becomes a dynamic burn-in test state and the second internal circuit 404 becomes a static burn-in test state. During the burn-in test, when the switch circuit 402 is switched and set to a state where the output signal of the oscillation circuit 401 is propagated to the signal lines 415 and 416, the first internal circuit 403 becomes a static burn-in test state and the second internal circuit 404 becomes a dynamic burn-in test state. In this manner, by switching the switch circuit 402, the dynamic burn-in test and the static burn-in test can be alternately performed during the burn-in test.
Further, Patent document 2 (Japanese Unexamined Patent Application Publication No. 62-204171) discloses a technique to perform switching between a dynamic burn-in test and a static burn-in test by using a timer.